The present invention relates to devices for performing an anesthesia procedure.
During childbirth, paracervical and trans-pudendal anesthesia procedures are commonly used to reduce pain during the first and second stages of labor. The first stage of labor may be defined as the period of time between the onset of labor and the time at which the cervix has completely dilated. The second stage of labor takes place between the time at which the cervix has completely dilated and the time of child delivery. Pain during the first stage of labor is primarily caused by effacement and dilation of the cervix, and may be relieved by a paracervical block. Pain during the second stage of labor results from dilation of the vagina, pressure exerted against the pelvic bones, and episiotomy, and may be relieved with a pudendal block.
The paracervical anesthesia procedure is normally performed when the cervix has dilated approximately 4 centimeters, with uterine contractions taking place at approximately 5 minute intervals and lasting at least 30 seconds. The paracervical block may be either a single injection or a continuous type, and is performed to block the nerves around the cervical opening.
During the procedure, the physician inserts a needle and catheter assembly into the vagina with the needle retracted within the assembly, and places the distal end of the assembly against the ligament at the vaginal fornix immediately lateral to its junction with the cervix. Next, the needle is pushed out of the assembly by the physician, and should penetrate the mucosa approximately 1.0 to 1.5 centimeters, after which the anesthetic solution is injected through the needle into the mucosa. In this manner, the anesthetic solution may be injected at 3 or 4 and 8 or 9 o'clock positions into the mucosa around the cervix to obtain the paracervical block.
When the cervix has almost fully dilated, the transpudendal anesthesia procedure is performed to relieve pain during the second stage of labor. In this procedure, the anesthetic solution is injected into the wall of the vagina.
During the paracervical anesthesia procedure, care must be taken to prevent over penetration of the needle or assembly in the mucosa, resulting in possible harm or death to the infant. When the physician pushes on a proximal end of the needle of present devices to penetrate the mucosa with the needle tip, the distal end of the assembly may become depressed into and stretch the mucosa. Consequently, the needle tip and possibly the distal portion of the assembly may pass through the mucosa. Also, the distal end of the assembly may slip while the physician applies force to the needle, causing the needle to penetrate the body at the wrong location. In certain of the present devices, the needle may slip from the assembly while the assembly is being positioned, resulting in needle penetration before the assembly has been properly placed for performing the procedure.